Gear Shifting Apllication

1

A REPORT ON

“GEAR SHIFTING APPLICATION”

Prepared By:

PANCHAL ANKIT (06 ME 23)

PANCHAL JAWAL (06 ME 24)

DEPARTMENT OF MECHATRONICS AND MECHANICAL ENGINEERING,

U.V.PATEL COLLEGE OF ENGINEERING,

GANPAT UNIVERSITY

GANPAT VIDYANAGAR,

KHERVA.

2010

2

A REPORT ON

“GEAR SHIFTING APPLICATION”

A PROJECT REPORT SUBMITTED IN PARTIAL FULFILLMENT OF

THE REQUIREMENTS FOR THE DEGREE OF

BACHELOR OF TECHNOLOGY

(MECHANICAL ENGINEERING)

BY

PANCHAL ANKIT (06 ME 23)

PANCHAL JAWAL (06 ME 24)

UNDER THE GUIDANCE OF

MR. TUSHAR SHAH

AT THE

U.V.PATEL COLLEGE OF ENGINEERING,

GANPAT UNIVERSITY,

GANPAT VIDYANAGAR, KHERVA

2010

3

CERTIFICATE

This project work is the bonafide work done by following students of VIII semester of

Mechanical Engineering Department of U. V. Patel College of Engineering, under the

guidance of Mr. P. G. Halvadia towards the partial fulfillment of the requirements for the

Degree of Bachelor of Technology (Mechanical) of Ganpat University, Ganpat Vidyanagar.

NAME : EXAM NO. (1) PANCHAL ANKIT 526

(2) PANCHAL JAWAL 527

Guide : ______________________________

Internal Examiner: ____________________

External Examiner: ____________________

Head of Department: ___________________ (ME/MC Dept.)

4

CERTIFICATE

This project work is the bonafide work done by PANCHAL ANKIT N, Roll No. 06 ME 23,

student of VIII semester of Mechanical Engineering Department of U. V. Patel College of

Engineering, under the guidance of Mr. Tushar Shah towards the partial fulfillment of the

requirements for the Degree of Bachelor of Technology (Mechanical) of Ganpat University,

Ganpat Vidyanagar.

Guide : ______________________________



Head of Department: ___________________

5

CERTIFICATE

This project work is the bonafide work done by PANCHAL JAWAL J, Roll No. 06 ME 24,

student of VIII semester of Mechanical Engineering Department of U. V. Patel College of

Engineering, under the guidance of Mr. Tushar Shah towards the partial fulfillment of the

requirements for the Degree of Bachelor of Technology (Mechanical) of Ganpat University,

Ganpat Vidyanagar.

Guide : ______________________________



Head of Department: ___________________

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ACKNOWLEDGEMENTS

We would like to express sincere thanks to our project guide Mr Tushar Shah for their

guidance and support throughout the duration of the balancing wheeled robot project. We have

learned a lot under their guidance, be it practically or theoretically.

We would also specially like to thank Mr B. P. Patel for giving all the valuable help in

development of our project. We would also like to thank all the faculty members of our

department.

We are undoubtedly indebted to all our friends and relatives, for physically and

emotionally supporting us through all the stages of the huge task at hand. Equal thanks to all

friends & classmates for their invaluable inputs and creative ideas, without whom this work

would be a meaningless contraption.

Panchal Ankit N (06ME23)

Panchal Jawal J (06ME24) Date:31/05/2010

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ABSTRACT

In automobiles, the engine is a variable drive which transmits power. So gear box is

necessary to get required speed and torque. So the main concept of manual gear shift is to shift

the gear at a specific rpm in order to get maximum speed and torque.

A manual transmission, also known as a manual gearbox or standard transmission is a

type of transmission used in motor vehicle applications. It generally uses a driver-operated

clutch, typically operated by a pedal or lever, for regulating torque transfer from the internal

combustion engine to the transmission, and a gear-shift, either operated by hand (as in a car) or

by foot (as on a motorcycle). Other types of transmission in mainstream automotive use are the

automatic transmission, semi-automatic transmission, and the continuously variable transmission

(CVT).

A four-speed transmission is a transmission that allows a vehicle to operate at four

different speeds. This was an improvement on earlier transmissions, because it enabled the

vehicles that used the four-speed transmissions to run faster and better than the earlier

transmission systems. Most automobile vehicles today use the four-speed transmission.

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INDEX

Sr. No. Contents Page No. Acknowledgement 1 Abstract 2 Index 3 List Of Figure 5 List Of Table 6

1 Introduction 7 1.1 Unsynchronized Transmission 7 1.2 Synchronized Transmission 9 2 Concept 10 3 Project Components 11

3.1 230 V, AC Motor 12 3.2 Voltage Regulator 14 3.3 Friction Clutch 15 3.4 Gear Box 17

3.4.1 First Gear Shift 19 3.4.2 Second Gear Shift 20 3.4.3 Third Gear Shift 21 3.4.4 Fourth Gear Shift 22 3.4.5 Neutral Position 23

4 Calculations 24 4.1 Motor Power 25 4.2 Clutch design 26 4.3 Shaft Calculations 27

4.3.1 Shaft Specifications 28 4.3.2 Shaft 1 diameter 29 4.3.3 Shaft 2 diameter 30 4.4 Bearing Calculations 31

4.4.1 Bearing Specifications 32 4.4.2 Bearing 1(B1,B2,B5,B6) 33 4.4.3 Bearing 2(B3,B4) 34 4.5 Gears Calculation 35

4.5.1 Gear Teeth Calculation 35 4.5.2 Other Parameters 36 4.5.3 Gear Specifications 37 4.6 Speed Calculation 38

9

5 Benefits and Drawbacks of Manual Gear Shift 40 5.1 Benefits 40 5.2 Drawbacks 41 6 Applications and Popularity 43 7 Bibliography 44

LIST OF FIGURES

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Figure No. Figure Name Page No. 3.1.1 Single Phase AC Motor 12 3.1.2 Capacitor Arrangement 13 3.3.1 Multiplate Friction Clutch 15 3.4.1 Gear Box Arrangement 17

3.4.1.1 First Gear Shift 19 3.4.1.2 Second Gear Shift 20 3.4.1.3 Third Gear Shift 21 3.4.1.4 Fourth Gear Shift 22 3.4.1.5 Neutral Position 23

LIST OF TABLES

11

Table No. Table Description Page No.

4.5.3 Gear Spesicication Table 37 4.6 Speed Calculation Table 39

1. INTRODUCTION

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Manual transmissions are characterized by gear ratios that are selectable by locking

selected gear pairs to the output shaft inside the transmission. Conversely, most automatic

transmissions feature epicyclic (planetary) gearing controlled by brake bands and/or clutch packs

to select gear ratio. Contemporary automobile manual transmissions typically use four to six

forward gears and one reverse gear, although automobile manual transmissions have been built

with as few as two and as many as eight gears. Transmission for heavy trucks and other heavy

equipment usually have at least 9 gears so the transmission can offer both a wide range of gears

and close gear ratios to keep the engine running in the power band.

Manual gear shifting or manual transmissions come in two basic types: simple

unsynchronized systems where gears are spinning freely. Whereas the other one is the

synchronized systems, in which all gears are always in mesh but only one of these meshed pairs

of gears is locked to the shaft on which it is mounted at any one time, the others being allowed to

rotate freely; thus greatly reducing the skill required to shift gears.

1.1 Unsynchronized transmission

The earliest automotive transmissions were entirely mechanical unsynchronized gearing

systems. They could be shifted, with multiple gear ratios available to the operator, and even had

reverse. But the gears were engaged by sliding mechanisms or simple clutches, which required a

skilled operator who could use timing and careful throttle manipulation when shifting, so that the

gears would be spinning at roughly the same speed when engaged; otherwise the teeth would

refuse to mesh.

When upshifting to a higher gear, the speed of the gear driven by the engine had to drop

to match the speed of the next gear; as this happened naturally when the clutch was depressed, it

was just a matter of skill and experience to hear and feel when the gears could be persuaded to

mesh. However, when downshifting, the gear driven by the engine had to be sped up to mesh

with the output gear, requiring that the clutch be engaged so that the engine could be used to

speed up the gears; a technique called double declutching was used, which involved shifting the

transmission into neutral and speeding up the gears, then shifting from neutral into the lower

13

gear. In fact, such transmissions are often easier to shift from one gear to another without the use

of the clutch at all. The clutch, in these cases, is only used for starting from a standstill.

Even though automobile and light truck transmissions are now almost universally

synchronized, transmissions for heavy trucks and machinery, motorcycles, and for dedicated

racing are usually not. Non-synchronized transmission designs are used for several reasons. The

friction material, such as brass, in synchronizers is more prone to wear and breakage than gears,

which are forged steel, and the simplicity of the mechanism improves reliability and reduces

cost. In addition, the process of shifting a synchromesh transmission is slower than that of

shifting a non-synchromesh transmission. For racing of production-based transmissions,

sometimes half the teeth (or "dogs") on the synchros are removed to speed the shifting process,

at the expense of greater wear.

Heavy duty trucks use unsynchronized transmissions in the interest of saving weight.

Military edition trucks, which do not have to obey weight laws, usually have synchronized

transmissions, though this is also contingent upon the need for non trained personnel to be able

to operate them in emergencies. Highway use heavy-duty trucks in the United States are limited

to 80,000 pounds GVWR, and the lighter the curb weight for the truck, the more cargo can be

carried; with a synchronizer adding weight to a truck that could otherwise be used to carry cargo,

most drivers are simply taught how to double clutch, initially, and then most eventually gravitate

to shifting without the clutch. In the United States, traffic safety rules refer to non-synchronous

transmissions in classes of larger commercial motor vehicles. In Europe heavy duty trucks use

synchronized gearboxes as standard.

Similarly, most modern motorcycles use unsynchronized transmissions as synchronizers

are generally not necessary or desirable. Their low gear inertias and higher strengths mean that

forcing the gears to alter speed is not damaging, and the pedal operated selector on modern

motorcycles is not conducive to having the long shift time of a synchronized gearbox. Because

of this, it is necessary to synchronize gear speeds by blipping the throttle when shifting into a

lower gear on a motorcycle.

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1.2 Synchronized transmission

In a synchromesh gearbox, the teeth of the gears of all the transmission speeds are always

in mesh and rotating, but the gears are not directly rotationally connected to the shafts on which

they rotate. Instead, the gears can freely rotate or be locked to the shaft on which they are

carried. The locking mechanism for any individual gear consists of a collar on the shaft which is

able to slide sideways so that teeth or "dogs" on its inner surface bridge two circular rings with

teeth on their outer circumference; one attached to the gear, one to the shaft. (One collar

typically serves for two gears; sliding in one direction selects one transmission speed, in the

other direction selects the other) When the rings are bridged by the collar, that particular gear is

rotationally locked to the shaft and determines the output speed of the transmission.

Our working model is based on the unsynchronized transmission where four different

speeds are achieved using four gear shifts. Like other transmissions, a manual transmission has

several shafts with various gears and other components attached to them. Our project is

concerned with a rear-wheel-drive transmission system which has generally three shafts: an

input shaft, a countershaft and an output shaft. The countershaft is sometimes called a layshaft.

The other components are a speed regulator, a motor, a friction clutch and a gear box with eight

gears (4 gear ratios).

15

2. CONCEPT

16

3. PROJECT COMPONENTS

1. 230V, AC Motor

2. Voltage regulator

3. Friction clutch

4. Gear box with 8 gears

5. Speed displayer

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3.1 230 VOLTS, AC MOTOR

An AC motor is an electric motor that is driven by an alternating current. It consists of

two basic parts, an outside stationary stator having coils supplied with alternating current to

produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a

torque by the rotating field.

Figure 3.1.1 Single Phase AC Motor

There are two types of AC motors, depending on the type of rotor used. The first is the

synchronous motor, which rotates exactly at the supply frequency or submultiples of the supply

frequency. The magnetic field on the rotor is either generated by current delivered through slip

rings or by a permanent magnet. The second type is the induction motor, which runs slightly

slower than the supply frequency. The magnetic field on the rotor of this motor is created by an

induced current.

Induction motors are of two types based on the power supply: single phase and three

phase. In our project we are using the single phase motor.

In a single phase induction motor, it is necessary to provide a starting circuit to start

rotation of the rotor. If this is not done, rotation may be commenced by manually giving a slight

turn to the rotor. The single phase induction motor may rotate in either direction and it is only

the starting circuit which determines rotational direction.

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Figure 3.1.2 Capacitor connected in series with the startup winding of the motor

A capacitor is connected in series with the startup winding, creating an LC circuit which

is capable of a much greater phase shift (and so, a much greater starting torque). The capacitor

naturally adds expense to such motors. A capacitor ranging from 3 to 25 microfarads is

connected in series with the start windings and remains in the circuit during the run cycle. The

start windings and run windings are identical and reverse motion can be achieved by reversing

the wiring of the 2 windings, with the capacitor connected to the other windings as start

windings. By changing taps on the running winding but keeping the load constant, the motor can

be made to run at different speeds. Also, provided all 6 winding connections are available

separately, a 3 phase motor can be converted to a capacitor start and run motor by communing

two of the windings and connecting the third via a capacitor to act as a start winding.

19

3.2 VOLTAGE REGULATOR

A voltage regulator is an electrical regulator designed to automatically maintain a

constant voltage level. It may use an electromechanical mechanism, or passive or active

electronic components. Depending on the design, it may be used to regulate one or more AC or

DC voltages.

An AC voltage regulator is a type of household mains regulator which uses a

continuously variable autotransformer to maintain an AC output that is as close to the standard

or normal mains voltage as possible, under conditions of fluctuation. It uses a servomechanism

(or negative feedback) to control the position of the tap (or wiper) of the autotransformer,

usually with a motor. An increase in the mains voltage causes the output to increase, which in

turn causes the tap (or wiper) to move in the direction that reduces the output towards the

nominal voltage.

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3.3 FRICTION CLUTCH

A clutch is a mechanical device which provides driving force to another mechanism,

typically by connecting the driven mechanism to the driving mechanism. Its opposite component

is a brake, which inhibits motion. Clutches are useful in devices that have two rotating shafts. In

these devices, one shaft is typically attached to a motor or other power unit (the driving

member), and the other shaft (the driven member) provides output power for work to be done.

Figure 3.3.1 Multiplate Friction Clutch

In all vehicles using a transmission (virtually all modern vehicles), a coupling device is

used to separate the engine and transmission when necessary. The clutch accomplishes this in

manual transmissions. Without it, the engine and tires would at all times be inextricably linked,

and any time the vehicle stopped the engine would stall. Without the clutch, changing gears

would be very difficult, even with the vehicle moving already: deselecting a gear while the

transmission is under load requires considerable force, and selecting a gear requires the

revolution speed of the engine to be held at a very precise value which depends on the vehicle

speed and desired gear. In a car the clutch is usually operated by a pedal; on a motorcycle, a

lever on the left handlebar serves the purpose.

There are different designs of vehicle clutch, but most are based on one or more friction

discs, pressed tightly together or against a flywheel using springs. The friction material varies in

composition depending on whether the clutch is dry or wet, and on other considerations.

21

A multiplate clutch has several driving members interleaved with several driven

members. It is used in motorcycles, automatic transmissions and in some diesel locomotives

with mechanical transmissions. It is also used in some electronically controlled all-wheel drive

systems.

In our project we are using multiplate wet clutch. A wet clutch is immersed in a cooling

lubricating fluid, which also keeps the surfaces clean and gives smoother performance and

longer life. Wet clutches, however, tend to lose some energy to the liquid. Since the surfaces of a

wet clutch can be slippery (as with a motorcycle clutch bathed in engine oil), stacking multiple

clutch disks can compensate for the lower coefficient of friction and so eliminate slippage under

power when fully engaged.

22

3.4 GEAR BOX

On a conventional rear-drive transmission, there are three basic shafts; the input, the

output, and the countershaft. The input and output together are called the main shaft, since they

are joined inside the transmission so they appear to be a single shaft, although they rotate totally

independently of each other. The input length of this shaft is much shorter than the output shaft.

Parallel to the main shaft is the countershaft. There are a number of gears fixed along the

countershaft, and matching gears along the output shaft, although these are not fixed, and rotate

independently of the output shaft.

Figure 3.4.1 Gearbox Arrangement

A front-drive transmission is basically the same, but may be simplified. There often are

two shafts, the input and the output, but depending on the direction of rotation of the engine,

23

three may be required. Rather that input shaft driving the countershaft with a pinion gear, the

input shaft takes over the countershafts job, and the output shaft runs parallel to it. The gears are

positioned and engaged just as they are on the countershaft-output shaft on a rear-drive. This

merely eliminates one major component, the pinion gear.

In our project 4 different speeds will be produced from the set of eight gears arranged in

the gear box. The eight gears are mounted on the three shafts. First shaft contains the two gears

numbered as “1” & “2”, second contains 4 gears numbered as “3”, “4”, “5” & “6” and third

contains the remaining 2 gears numbered as “7” & “8”. The gears used are of different diameters

so that gear ratios can be varied and different speeds can be obtained. The movement of the

gears on the second shaft enables the meshing of gears.

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3.4.1 FIRST GEAR:

Let us now understand how four different speeds could be obtained from the set of eight

different gears. Meshing of 1st gear with 3rd and 5th gear with 7th gear will give the first gear

shift. This gear shift will give the maximum torque. The arrangement is shown in figure.

Figure 3.4.1.1 First Gear Arrangement

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3.4.2 SECOND GEAR:

Meshing of 2nd gear with 4th and 5th gear with 7th will give second gear shift. The speed

achieved will be higher than the previous gear shift whereas the torque will be comparatively

less. This arrangement is as shown below.

3.4.1.2 Second Gear Arrangement

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3.4.3 THIRD GEAR:

Now meshing of 1st gear with 3rd and 6th gear with 8th will give the third gear shift. The

obtain value of speed will be higher than that produced by first and second gear shift while the

torque obtained will be comparatively less. The arrangement of the third gear shift is as shown

below.

3.4.1.3 Third Gear Arrangement

27

3.4.4 FOURTH GEAR:

Finally meshing of gears 2nd with 4th and 6th with 8th will give the fourth gear shift. The

speed obtained here will be highest whereas the torque will be lowest. The arrangement of the

fourth gear shift is as shown in the figure.

3.4.1.4Fourth Gear Arrangement

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3.4.5 NEUTRAL: The gearbox will be in the neutral position if none of the gears are meshing. In the

neutral position no power is being transmitted and all the gears will be rotating ideally. The

arrangement of neutral gear shift is as shown below.

3.4.1.5 Neutral Position

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4.CALCULATIONS

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4.1 MOTOR POWER

The power required to drive the designed gear box will be calculated by the following

formula:

Power, P = (13.2 * 10¯³) *(K * z * v)*(1.55as) Watts

Where,

K = Material Factor = 1.88

z = No. of cutting edges in contact = 1

v = Cutting Speed in m/min = 55 m/min

a = Depth of Cut in mm = 0.6mm

s = Feed/Blade/Rev. in mm = 0.04 mm

ß = Machining Component

Therefore,

P = 97.1 Watts(Calculated Value)

P = 120 Watts(Standard Value)

Hence the standard value of motor with 120 Watts is taken into consideration.

Now, based on the power, the torque of required to rotate the gears is calculated.

Torque, τ = Power(P) / Angular Velocity(ω)

Where ω = 2 N / 60

Therefore, τ = 0.796 N.m

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4.2 CLUTCH DESIGN

In our project we have used the multiplate friction clutch whose internal and external

diameters are calculated as follows:

Transmitted Torque (Mt) = 0.8 N.m

Therefore Design Torque[Mt] = Kw * Mt

Where, Kw = Factor based on working condition

= K1 +K2 + K3 + K4

= 0.5 + 1.25 + 0.38 + 1.8

Hence, [Mt] = 3.14 N.m

Clutch Shaft Diameter Calculation:

d = [(49500*Kw*Kw) / (n [τ])]½

where, [τ] = allowable shear stress

= 700N/mm²

Therefore, d = 8.86mm

= 10mm(approx.)

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4.3 SHAFT CALCULATIONS

4.3.1 Shaft Specifications: Input shaft:- Diameter (d)= 10 mm Length (l) = 320 mm Intermediate shaft(spline):-

No. of spline = 6 Inner diameter = 10 mm Outer diameter = 15 mm Length (l) = 270 mm Output shaft:- diameter (d) = 10 mm length (l) = 320 mm

33

4.3.2 Shaft 1 Diameter:

Ra + Rb = F = τr(cos20) = 60N

ΣMa = 0

Therefore, Ra = 24.54N

And Rb = 35.45N

Mc = Mb = 50*35.45 = 1772.72

Now,

d³ = {(Kb*Mb)² + (Kt*Mt)³}

where,

[τ] = 127 N/mm² Kb = 2.25 Mb = 1772.72 N.mm Kt = 1.7 Mt = 800 N.mm d = 5.52 = 6 mm = 10 mm(standard)

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4.3.3 Shaft 2 Diameter:-

Ra + Rb = 192N

ΣMa = 0

Therefore, (192 * 65) – (110 * Rb) = 0

so, Ra = 78.55N And Rb = 113.48N

Mc = Mb = -113.45 * 45 = -5105.25

Now,

d³ = (16/ (π[τ])) * {(Kb*Mb)² + (Kt*Mt)³}

where, [τ] = 127 N/mm² Kb = 2.25 Mb= 5105.25 N.mm Kt = 1.7 Mt = 8640 N.mm Therefore, d = 9.07

= 10 mm(standard)

35

4.4 BEARING CALCULATIONS The bearings are mounted at the end of each of the shaft to ensure smooth moemn=ent of

the shaft when the gears are engaged. The bearings will help make movement of shaft smoother.

Here, we have used in total 6 bearings out of which 4 are identical and are connected to the ends

of the first and the third shaft where as the remaining two are connected to the ends of the

middle shaft. The selection of bearings is done by the following method.

4.4.1 Bearing specifications:-

• Bearing 1(B1, B2, B5, B6):-

B1 = B2 = B5 = B6 = 6300

inner dia. = 10mm outer dia. = 35mm width = 11mm

• Bearing 2(B3, B4):-

Bush:-

inner dia. = 11mm bearing outer dia. = 25mm total width = 16mm bearing width = 12mm

36

Bearing:-

B3 = B4 = 6305 (0.69 million rev.) outer dia. = 62mm inner dia. = 25mm width = 17mm

37

4.4.2 Bearing 1(B1,B2,B5,B6):

The deep groove ball type of bearings are selected. The calculation of the deep groove

ball bearings is shown below:

6000<= Co = 192 * 10

Assuming,

Fa/Co = 0.25

Therefore, e = 0.22 and Fa = 48N

Now, Fr = 64sin20

= 22N

And Fa = 0

Now, Fa/Fr <e

Therefore, P = XFr = 60N

For 6000, L = (C/P)³ = 0.216 mill. Rev.

For 6200, L = (C/P)³ = 0.296 mill. Rev.

For 6300, L = (C/P)³ = 1.157 mill. Rev.

So,

B1 = B2 = B5 = B6 = 6300

inner dia. = 10mm

outer dia. = 35mm

width = 11mm

38

4.4.3 Bearing 2(B3, B4):

Fr1 = Frsin20 = 22N

Fr2 = 92sin20 = 66N

Fr = Fr1 + Fr2

Therefore, Fr = 88N

Now,

P = XFr = 88N

L = (C/P)³

For 6005, L = 0.69

For 6205, L = 1.953

So,

B3 = B4 = 6305 (0.69 million rev.)

outer dia. = 62mm

inner dia. = 25mm

width = 17m

39

4.5 GEAR CALCULATON

4.5.1 Gear Teeth Calculation:

Assuming the number of teeth of first gear as 20 and taking the four speeds N1, N2, N3,

N4 as 150, 300, 600, 1200 respectively. Hence the required dimensions of the remaining gears

are calculated as follows:

Let,

T1,T2,Tз……T8 = no. of teeth of gears 1,2,3….8 respectively.

Now,

T1/T3 = 300\1200

Given that, T1 = 20

Hence, T3 = 80

Again,

T2 + T4 = 100 and

T2\T4 = 600\1200 = 0.5

Hence, T4 = 2T2

Therefore, T2 = 33.33 = 34 and T4 = 66

Assuming number of teeth on gear 5 as 20, the number of teeth of the respective gears

will be found out as follows:

Assume T5 = 20

Hence, T5\T7 = 150\300 = 0.5

40

Therefore, T7 = 40

Again,

T6 + T8 = 60 and

T6\T8 = 600\300 = 2

Therefore, T6 = 40 and

T8 = 20.

4.5.2 Other Parameters:

The module of the first four gears is taken as 1.25 while the remaining four gears is taken

as 2. Based on the module and the number of teeth, the pitch circle diameter, addendum

diameter, dedendum diameter, clearance and tooth thickness is found out from the empirical

formula as shown below. Considering 20 degree full depth system, the empirical formula in

terms of module (m) is given below:

Pitch Circle Diameter = m * No. of Teeth

Addendum = m

Dedendum = 1.25m

Clearance = 0.25m

Tooth thickness = 1.5708m

Fillet radius = 0.4m

41

The table shows the required dimensions of each of the gears used to transmit required

amount of speed:

Table 4.5.3 Gear Specifications

Gear no. 1 2 3 4 5 6 7 8

No. of teeth 20 34 80 66 20 40 40 20

Pitch circle diameter

25 42.5 100 82.5 40 80 80 40

Addendum diameter

26.25 43.75 101.25 83.75 42 82 82 42

Dedendum diameter

23.44 41 98.5 81 37.5 77.5 77.5 37.5

Clearance 0.3125 0.3125 0.3125 0.3125 0.5 0.5 0.5 0.5

Tooth thickness

1.9635 1.9635 1.9635 1.9635 1.9635 1.9635 1.9635 1.9635

Fillet radius 0.5 0.5 0.5 0.5 0.8 0.8 0.8 0.8

Tooth width 12.5 12.5 12.5 12.5 20 20 20 20

42

4.6 SPEED CALCULATION

The speed of the four gear shifts are assumed as 150, 300, 600, 1200. The assumption is

made in order to find out the number of teeth of the gears. Now, the assumed speed will be

checked by following formula as follows:

N1 = 1200*(T1\T3)*(T5\T7)

= 1200*(20\80)*(20\40)

= 150 rpm

N2 = 1200*(T2\T4)*(T5\T7)

= 1200*(34\66)*(20\40)

= 300 rpm

N3 = 1200*(T1\T3)*(T6\T8)

= 1200*(20\80)*(40\20)

= 600rpm

N4 = 1200*(T2\T4)*(T6\T8)

= 1200*(34\66)*(40\20) = 1200 rpm

43

Now, the difference between the assumed speed and the actual speed is found out and

checked whether the assumption made is satisfactory or not. The following table shows the

difference between the assumed speeds and the actual speed and the percentage difference

between them.

Table 4.6 comparison of actual and calculated speeds

Speed Std. speed Calculated Difference Percentage

N1 150 150 0 0

N2 300 309.1 +9.1 3.03

N3 600 600 0 0

N4 1200 1236.4 +36.4 3.03

44

5. BENEFITS AND DRAWBACKS OF MANUAL GEAR SHIFT

5.1 Benefits

Manual transmissions generally offer better fuel economy than automatic torque

converter transmissions; however the disparity has been somewhat offset with the introduction

of locking torque converters on automatic transmissions. Increased fuel economy with a properly

operated manual transmission vehicle versus an equivalent automatic transmission vehicle can

range from 5% to about 15% depending on driving conditions and style of driving. Manual

transmissions do not require active cooling and generally weigh less than comparable

automatics. The manual transmission couples the engine to the transmission with a rigid clutch

instead of a torque converter which slips by nature. Manual transmissions also lack the parasitic

power consumption of the automatic transmission's hydraulic pump.

Manual transmissions also generally offer a higher selection of gear ratios. Many

vehicles offer a 5-speed or 6-speed manual, whereas the automatic option would be a 4-speed all

the way up to (more recently) an 8-speed. The higher selection of gears allowed for more uses of

the engine's power band, allowing for higher fuel economy and power output. This is generally

due to the space available inside of a manual transmission versus an automatic since the latter

requires extra components for self-shifting, such as torque converters and pumps.

Manual transmissions are more efficient than conventional automatics and belt-driven

continuously-variable transmissions. The driver has more direct control over the car with a

manual than with an automatic, which can be employed by an experienced, knowledgeable

driver who knows the correct procedure for executing a driving maneuver, and wants the vehicle

to realize his or her intentions exactly and instantly. When starting forward, for example, the

driver can control how much torque goes to the tires, which is useful on slippery surfaces such as

ice, snow or mud. This can be done with clutch finesse, or by starting in second gear instead of

first. An engine coupled with a manual transmission can often be started by the method of push

starting. This is particularly useful if the starter is inoperable or defunct. Likewise, a vehicle with

a manual transmission and no clutch/starter interlock switch can be moved, if necessary, by

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putting it in gear and cranking the starter. This is useful when the vehicle will not start, but must

be immediately moved e.g. off the road in the event of a breakdown, if the vehicle has stalled on

a railway crossing, or in extreme off-roading cases such as an engine that has stalled in deep

water.

Currently only fully manual transmissions allow the driver to fully exploit the engine

power at low to medium engine speeds. This is due to the fact that even automatic transmissions

which provide some manual mode use a throttle kickdown switch, which forces a downshift on

full throttle and causes the gearbox to ignore a user command to upshift on full throttle. This is

especially notable on uphill roads; where cars with automatic transmission need to slow down to

avoid downshifts, whereas cars with manual transmission and identical or lower engine power

are still able to maintain their speed.

In contrast to most manual gearboxes, most automatic transmissions have a free-wheel-

clutch. This means that the engine does not slow down the car when the driver steps off the

throttle. This leads to more usage of the brakes in cars with automatic transmissions.

5.2 Drawbacks:

The smoothness and correct timing of gear shifts are wholly dependent on the driver's

experience and skill; because the driver selects each gear, it is also possible to select the wrong

gear. Attempting to select reverse while the vehicle is moving forward causes severe gear wear

(except in transmissions with synchromesh on reverse when the vehicle is moving backward),

and choosing a low gear with the car moving at speed can overspeed and damage the engine.

There is a learning curve with a manual transmission; the driver must develop a feel for properly

engaging the clutch, especially when starting forward on a steep road or when parking on an

incline.

Some automatic transmissions can shift ratios faster than a manual gear change can be

accomplished, due to the time required for the average driver to push the clutch pedal to the floor

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and move the gearstick from one position to another. This is especially true in regards to dual

clutch transmissions, which are specialized computer-controlled manual transmissions.

Manual transmissions place a slightly greater workload on the driver in heavy traffic

situations, when the driver must often operate the clutch pedal. In comparison, automatic

transmissions merely require moving the foot from the accelerator pedal to the brake pedal, and

vice versa. Manual transmissions require the driver to remove one hand periodically from the

steering wheel while the vehicle is in motion.

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6. APPLICATIONS AND POPULARITY

Many types of automobiles are equipped with manual transmissions. Small economy cars

predominantly feature manual transmissions because they are cheap and efficient, although

many are optionally equipped with automatics. Economy cars are also often powered by very

small engines, and manual transmissions make more efficient use of the power produced.

Sports cars are also often equipped with manual transmissions because they offer more

direct driver involvement and better performance. Off-road vehicles and trucks often feature

manual transmissions because they allow direct gear selection and are often more rugged than

their automatic counterparts.

Conversely, manual transmissions are no longer popular in many classes of cars sold in

North America, Australia and Asia, although they remain dominant in Europe and in Latin

America. Nearly all cars are available with an automatic transmission option, and family cars

and large trucks sold in the US are predominantly fitted with automatics. In Europe most cars are

sold with manual transmissions. Most luxury cars are only available with an automatic

transmission. In most cases where both transmissions are available for a given car, automatics

are an at cost option, but in some cases the reverse is true.

In some places (Estonia, Finland, France, Germany, Ireland, Israel, Netherlands, Norway,

Singapore, South Korea, Sweden, Turkey and the UK), when a driver takes the licensing road

test using an automatic transmission, the resulting license is restricted to the use of automatic

transmissions. This treatment of the manual transmission skill seems to maintain the widespread

use of the manual transmission. As many new drivers worry that their restricted license will

become an obstacle for them where most cars have manual transmissions, they make the effort to

learn with manual transmissions and obtain full licenses. Some other countries (such as India,

Pakistan, Malaysia, Slovenia, Serbia, Brazil and Denmark) go even further, whereby the license

is granted only when a test is passed on a manual transmission. In Denmark you are allowed to

take the test on an automatic if you are handicapped, with such license you will not be able to

drive a manual transmission.

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7. BIBLIOGRAPHY Reference books: 1. Design Data Book 2. Elements of machine design by V B Bhandari

References sites: 1. www.aboutconstruction.com 2. www.howstuffworks.com

Gear Shifting Apllication

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